This invention relates generally to abrasive and wear resistant surfaces and articles comprising these surfaces. More specifically, it discloses new and improved methods for obtaining such surfaces containing non-randomly distributed hard particles that provide abrasive and wear resistant quality to the surfaces.
U.S. Pat. Nos. 4,925,457; 5,092,910; and 5,049,165 as well as 5,380,390; 5,203,880; 5,190,568; 5,817,204; 5,620,489; 5,991,330; and 5,980,678, all of which are incorporated herein by reference, all teach methods for providing a uniform distribution of hard particles in a non-random manner on the surface of an abrasive article.
International Publication WO 98/51448 discloses placing a perforated stencil or mask against a tool preform so that the perforations define cavities, filling and packing these cavities with a metal braising composition in the form of paste and then removing the stencil leaving discrete particles of braising paste tacked to the cutting surface. Hard particles (abrasive grains) are deposited onto the paste particles or pre-mixed with paste particles and fixed in place by firing the preform at braising conditions.
In U.S. Pat. Nos. 5,380,390; 5,817,204; and 5,980,678, all of which are incorporated herein by reference, various adhesive materials and at least one mask are used for forming a non-uniform distribution of and for holding hard particles on substrates and/or carriers prior to thermal processing of the composite abrasive material. For example, an abrasive material can be formed by coating a substrate with an adhesive, placing a mask over the adhesive coated substrate, contacting this substrate with a quantity of hard, abrasive particles so that the particles pass through the openings of the mask and adhere to the substrate, and then removing all of the plurality of the particles not held by the adhesive and optionally also removing the mask. The particles remaining in a pattern in the substrate are then surrounded with a sinterable or fusible matrix material while the particles are temporarily held by the adhesive. Subsequent treatment with heat and/or pressure completes the abrasive material.
The mask may take a form of a mesh or other cellular material that is placed against the substrate before contacting the substrate with the hard particles. The mask will then determine the distribution of the hard particles and/or zones or clusters of the particles according to the openings of the mesh or other cellular material. Further, the mask can be removed prior to heating or left to become an integral part of the abrasive material. Moreover, as described in the patents, the substrate can be a preform of sinterable matrix material and the hard particles can be urged or compacted into it with various compressing means, such as roll compaction of the pre-positioned hard particles before sintering of the material.
As further noted in the patents, the matrix material can be a sinterable or fusible material and can be deposited by a temperature related process such as thermal (e.g., plasma) spray or vapor deposition, thermal deposition of material being considered an equivalent of sinterable material. As a variation of sintering, the matrix material may also be impregnated with a fusible material by placing a fusible material on at least one side of the assembly before beginning the heating/or compaction, the fusible material melting during heating and being carried into the matrix material by capillary action.
U.S. Pat. No. 5,620,489, which is incorporated herein by reference, discloses a sinterable matrix material in the form of a soft, easy deformable and flexible preform made from a mixture of a quantity of powdered sinterable matrix material and a liquid binder composition. A plurality of abrasive particles can then be included at least partially in the preform which is then sintered to form an abrasive article. For example, the binder-powder mixture can be dispensed onto a support surface, and doctored to uniform thickness by a doctor blade for forming the preform. The plurality of abrasive particles can be included in the perform, e.g., by placing the particles on at least one side of the preform and then urging the particles into the preform. The abrasive particles can be urged into the preform before the preform is sintered or during sintering. Moreover, the particles can be included in the preform in a random manner or in a non-random manner that can be defined by a cellular type mesh or mask material.
U.S. Pat. No. 5,791,330, which is incorporated herein by reference, relates to similar abrasive materials having a non-random distribution of abrasive particles and teaches that the mesh material, after being used to position the abrasive particles, may be partially or completely removed either physically prior to sintering the matrix material, or dissolved or evaporated at the temperature used to sinter the matrix material leaving the abrasive particles uniformly distributed within matrix material. The patent also discloses that structural members can be positioned between or at least on one side of the matrix material, abrasive particles, and mesh materials and can be of metallic or non-metallic compounds, powder, fibers, meshes, shims, foils and any combinations thereof. The composition of the structural members can be different from the composition of the matrix material and they can be sintered or brazed, preferably under pressure, to the sintered abrasive material. The patent also discloses as suitable sinterable matrix materials or a component of sinterable matrix materials, compositions comprising carbide forming elements, such as boron, chromium, iron with zinc and without zinc and that braising and fusing materials can be used as additives with the compositions.
The present invention provides a new and improved method for making articles, including but not limited to abrasive and wear resistant articles containing hard, abrasive particles distributed in a desired, preferably non-random or non-uniform pattern in the articles that is more suitable for mechanization, automation, and mass production.
In accordance with the invention, there is provided. a method for making an abrasive material comprising a plurality of hard particles providing the abrasive quality distributed in a retaining matrix for holding said particles in place, said method comprising the steps of placing a mask having openings therein against a carrier capable of supporting a plurality of said particles, providing affixing means on an outer side of said mask remote from said carrier to which hard particles will adhere, applying a plurality of particles to said outer side of said mask so that a portion of the particles pass through the openings of the mask and form a pattern of said particles on said carrier corresponding to the openings of the mask and another portion of the particles adhere to said mask, separating the mask containing the hard particles adhered to if from the carrier leaving the pattern of said particles on the carrier, at least partially surrounding the particles on the carrier with a retaining matrix material, and heating said retaining matrix material to cause said material to form a retaining matrix that holds said particles in said pattern.